5th wheel design

[skyking]

Here is the first sketch of the trailer.
It has a roof that pops up 18"~24". I have not finalized anything, so the heights are still 'soft'.
Interior height is 70" collapsed, 88"~94" raised.
It has adaptive suspension that can raise it up 6" for driveways, railroad crossings, etc. This allows for a low 6~8" ground clearance at highway speeds.
I have pages of floor plan in my head, but that does not affect aerodynamics.
It will be faired very closely to the tow vehicle with movable fairings. Tow vehicle height is 72", trailer is 90" as shown.
Trailer starts at 80" wide to match tow vehicle wake. That may be changed with advice from aerohead and others. It tapers to 96" but I would happily start out wider if I can be convinced the drag penalty could be minimized.
Radii will not be true radii, but constructed with ~1" slices of plywood to approximate one.
I've been conflicted about building it 102" wide. Wider = more drag, and several states have areas with 96" maximium widths. 102" would give me a little more room to plan with.

[slowmover]

Either width is okay on a big road which itself has no problems. But 96" is much easier to live with, intuitively, on two-laners with no shoulders, turns in small towns, fuel stops, and many rv parks/campsites, IMO. This is true even with 20' construction trailers I've noticed with others towing: crossing over into another lane w/o quite being aware of just how far over. Granted this tendency is reduced with a 5'er/GN hitch arrangement.

You've set yourself an impressive set of design goals.

Will you're be going with onboard air (such as KILBY or VMAC) for fairly fast, high-powered suspension-height changes. Air tanks near the trailer front?

Sure am looking forward to this. Will the present Avion be the "donor vehicle"?

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[skyking]

I've thought about and rejected the donor vehicle concept. I want the latest tech and appliances in this new rig.
For example, I'd install a danfoss compressored AC/DC marine fridge/freezer without the LP hassles. 16 gallon water heater, Solar panel system, super efficient heat pump.
I'll leave the compressor in the tow rig and put a tank in the trailer, along with the control valves. It would either have automatic or manual setting. I can get speed information from the VSS signal on my PCM. Once the speed drops below 10 MPH, I could have it go to a high position.
I am settling on the 96" width for all those reasons you mentioned, and also due to the length.
The really cool part is the weight savings. I'm trading labor and higher cost materials for weight. I have a goal of around 6000 pounds dry

[slowmover]

Thanks for the info. There are some very good discussions on AIR about trailer construction materials for the interior, floor, insulation, etc, that may be of interest to you. Nyloboard is one: as subfloor; weighs more but is rotproof and may have better dimensional stability than marine plywood or OSB (Advantech). Same for some honeycomb materials that are lighter.

There's a trade-off somewhere with weight and aero, but I don't know where it is (converging lines on a graph). Given that one is not in mountainous terrain constantly, or in stop-n-go traffic, the "weight penalty" doesn't mean much inside some parameters the truck can live with in re weight as one runs the roads (mainly gearing and engine power graphs). If you hit 6k, great, but I sure wouldn't sweat 7,500-lbs as the final result as I really (really) think it won't make much difference.

On mine (305/555) there just isn't much difference from 9k to 11k for a given rig. Or, from 6k to 8k. (The latter set is only slightly better). The "killer" on the former is that it is getting up to factory recommended limits (conventional pull), thus any stops exact a telling penalty. On-highway it is almost nil (in generally level terrain) overall, given one is at a happy rpm. A change to 4.10 would take care of it were another set of gears for the NV-5600 available. Or a seven speed with two overdrive choices.

Gotta love a Cummins with a turbocharger!!

Have you finalized the truck spec for a given combination weight? A man trans might widen the performance envelope with a rear gear change, for instance.

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[skyking]

It will be the truck I have now, most likely. It performs fine with the current 5th wheel, so a lighter, vastly more aerodynamic one should be a real pleasure.

[slowmover]

Will the truck receive any aero/mechanical/gear/electronic or other FE-minded changes to establish a new solo baseline?

The current percentage mpg drop from solo to towing, at present, is . . . ?

Thanks

[aerohead]

if the 'rear' of the tow vehicle and 'front' of trailer are 'matched'( however you can do that ),and if the gap were sealed,as in the graphic,there would be no pressure on the front of the trailer.It would be in a full draft.
That would be getting off to a really good start.

[skyking]

Originally Posted by aerohead

if the 'rear' of the tow vehicle and 'front' of trailer are 'matched'( however you can do that ),and if the gap were sealed,as in the graphic,there would be no pressure on the front of the trailer.It would be in a full draft.
That would be getting off to a really good start.

It will be in line with no more than a 2" gap between. The bed of the truck will be ~4" below the projecting part of the trailer. That will be the biggest gap.

What do you think of the rear profile as I have it?
The initial 9 degree slope fits the requirements of the floor plan. The 2nd, 12 degree increase to 21 degrees is totally arbitrary. I can steepen or shallow that one up, it is over mechanicals and storage. Everything aft of that vertical line, the side taper and roof taper can be changed.
I can construct those 75" transition radii from 0 to 9 and 9 to 21 degrees without too much difficulty. I hope that will keep things better attached than a hard angle.

Slowmover, the truck is getting 22 now, and 13 with the current 5th wheel. That's about a 41% drop.
There are several economy mods underway, but no time to either finish them or test them for a few months. Mostly it sits while I work 6 tens.
I have an active grille control in the works, electric cooling fans, rear wheel fairing, 75% belly pan, new bumper and front spoiler all planned.

[aerohead]

Originally Posted by skyking

It will be in line with no more than a 2" gap between. The bed of the truck will be ~4" below the projecting part of the trailer. That will be the biggest gap.

What do you think of the rear profile as I have it?
The initial 9 degree slope fits the requirements of the floor plan. The 2nd, 12 degree increase to 21 degrees is totally arbitrary. I can steepen or shallow that one up, it is over mechanicals and storage. Everything aft of that vertical line, the side taper and roof taper can be changed.
I can construct those 75" transition radii from 0 to 9 and 9 to 21 degrees without too much difficulty. I hope that will keep things better attached than a hard angle.

Slowmover, the truck is getting 22 now, and 13 with the current 5th wheel. That's about a 41% drop.
There are several economy mods underway, but no time to either finish them or test them for a few months. Mostly it sits while I work 6 tens.
I have an active grille control in the works, electric cooling fans, rear wheel fairing, 75% belly pan, new bumper and front spoiler all planned.

If she were mine,I'd find the elevation of the 'Template,'based on the trailer at that distance back and fix it there.You ought to be able to get to Mair's 22-degrees by that distance ( just shootin' from the hip ).
I think you'll have separation as you make the jump from 9-degrees but the flow will re-attach.
For 2012,Honda,Porsche,Aston Martin,Ferrari,AUDI,Lamborghini,and others are using the 'Template' and I think we're going to see more,rather than less of it.
I'd stay as close to it as I could.

[slowmover]

Slowmover, the truck is getting 22 now, and 13 with the current 5th wheel. That's about a 41% drop.
There are several economy mods underway, but no time to either finish them or test them for a few months. Mostly it sits while I work 6 tens.
I have an active grille control in the works, electric cooling fans, rear wheel fairing, 75% belly pan, new bumper and front spoiler all planned.

This is going to be an exciting truck/trailer project!!

I look forward as the time/money equation starts to work for me to do some similar stuff on my tow vehicle as you have outlined on yours, but with a conventionally-hitched trailer in mind.